<form action="" method="post"> 
<table>
	<tr>
		<td>
		Nhap chuoi
		</td>
		<td>
		<input type="text" name="ma">
		</td>
	</tr>
	<tr>
		<td>
		</td>
		<td>
		<input type="submit" value="ok">
		</td>
	</tr>
</table>
</form>
<?php
echo md5($_POST['ma']);
?>